This invention relates to a luminaire lens assembly which is particularly suited for indoor applications such as retail store, restaurant and warehouse illumination as well as general industrial applications.
Retail stores and restaurants require even, uniform, lighting which is adequate for operation while subtle enough not to create unwanted glare. Uniform lighting should illuminate all areas with a consistent dispersed light. The use of larger, more powerful lights is becoming more prevalent in large scale restaurants and retail stores where large open spaces must be illuminated. This must be achieved however without creating a xe2x80x9cfootballxe2x80x9d field effect or expressly over lighting any one area.
Warehouse facilities also require uniform lighting which is energy efficient yet capable of fully illuminating the appropriate areas for everyday operation. In large warehouses using forklift truck inventory movement, the forklift drivers must be able to read labels on the inventory from their seats. This makes good vertical and horizontal illumination especially important. In some facilities, the inventory is stacked three to four feet high on skids. The skids are then piled three high, which means drivers may be reading product labels as high as 15 feet off the floor.
As the commercial trend moves to larger retail and restaurant facilities which require lighting more similar to historical industrial lighting systems, a solution is needed which provides industrial style lighting modified for retail, restaurant and warehouse applications. A luminaire assembly in combination with an efficient lighting unit is needed.
An improved luminaire lens assembly should provide uniform lighting, minimum perceived glare to those working under the system and a reduction in any potentially dark areas below the system. The improved luminaire lens assembly should make use of refracting prismatic lenses in combination with adequate reflective lenses to create the desired illumination while achieving an aesthetically pleasing luminaire.
It is a principal object of the present invention to provide a luminaire lens assembly which produces uniform lighting with minimum glare by using a combination of reflective and refractive lenses.
It is a further object of the present invention to provide a luminaire lens assembly using equally spaced and equally sized prisms in luminaire lenses to allow the light passing through the prisms to illuminate without being significantly reduced in intensity or significantly lost by refraction.
It is still a further object of the present invention to provide a luminaire lens assembly using a bottom refractive lens having an internal refractive area which utilizes a stepped down system for arranging the refractive prismatic areas.
In carrying out the above objects, features and advantages of the present invention, the present invention provides a luminaire lens assembly with a top lens having an external reflecting area and a bottom lens including an external refracting area and an internal refracting area. The internal refracting area has at least three concentric prismatic areas. A first concentric prismatic area having a first defined number of prisms, a second concentric prismatic area disposed directly adjacent the first concentric area having a second defined number of prisms at least 1.5 times as great as the first defined number of prisms, and a third concentric prismatic area disposed directly adjacent the second concentric area having a third defined number of prisms at least 1.5 times as great as the second defined number of prisms. In addition the first concentric prismatic area defines a radius and the second concentric prismatic area defines a second radiuus at least 1.5 times as great as the first concentric prismatic radius. The third concentric prismatic area defines a third radius which is at least 1.5 times as great as the second concentric prismatic radius.
In the preferred embodiment, the number of prisms in the next adjacent concentric prismatic area is always twice as great as the number of prisms in the preceding concentric prismatic area and the radius of the next adjacent concentric prismatic area is always twice as great as the radius of the preceding concentric prismatic area.
It is yet another object of the present invention to provide a luminaire lens assembly having top lens with an annular portion including a first section and a second section where the first section is disposed adjacent the bottom lens and defined by a radius Rr1 and second section defined by a radius Rr2 where Rr2 is greater than Rr1 by a ratio in a range from 0.5 to 5.0.
It is still a further object of the present invention to provide a luminaire lens assembly having a top lens with an external reflecting area. The bottom lens includes an external refracting area and an internal refracting area. The internal refracting area has at least three concentric prismatic areas, a first concentric prismatic area having a first defined number of prisms, a second concentric prismatic area disposed directly adjacent the first concentric area having a second defined number of prisms at least 1.5 times as great as the first defined number of prisms, and a third concentric prismatic area disposed directly adjacent the second concentric area having a third defined number of prisms at least 1.5 times as great as the second defined number of prisms. The first concentric prismatic area also defines a radius. The second concentric prismatic area further defines a second radius which is at least 1.5 times as great as the first concentric prismatic radius. The third concentric prismatic area still further defines a third radius which is at least 1.5 times as great as the second concentric prismatic radius. The external refracting area includes a plurality of concentric prisms, each prism including a first prism wall and a second prism wall, whereby the first prism wall defines an angle A to the central axis Xc of the luminaire lens assembly and the second prism wall defines an angle B to the central axis Xc of the luminaire lens assembly and the relationship between angle A to x is A=0.0114x2xe2x88x920.1071x+3.5158 and the relationship between angle B to x is B=xe2x88x920.0012x2xe2x88x920.4468x+69.458 and x is the prism number from the perimeter of the bottom lens.
The above objects and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.